Thermae Bath Spa, Bath, England

Issue 33 Oct / Nov 2006 : Retail : Spa

Architect: GRIMSHAW Lighting Design: SPEIRS AND MAJOR ASSOCIATES

Five years late and up to £30 million over budget (nothing to do with the lighting!), Thermae Bath Spa has been labelled the ‘Scottish Parliament of the South’ for all the problems it encountered. But when it finally opened its doors to intense media and public interest, it was a big hit for most. Claudia Clements of Speirs and Major Associates explains the role of the lighting design in the project.

In early August 2006, the Thermae Bath Spa project opened its doors to the public. The new Spa offers visitors bathing in the natural thermal waters and is housed in a mix of new build and sensitively restored historic listed buildings. The New Royal Bath is a contemporary stone cube contained within a glass skin. It houses two pools and an existing grade 1 listed building forms its entrance. The new building connects to John Wood’s Hot Bath built in 1775 which is the source of the spa waters and has a sunken pool at its heart. The 1783 Cross Bath provides open air bathing and a dramatic focus at the end of Bath Street colonnade. The project was developed and funded by Bath & North East Somerset Council in association with The Millennium Commission and Thermae Development Company. Grimshaw and conservation architects’ Donald Insall Associates worked on the project. Speirs and Major Associates designed the specialist lighting design to all public areas and Arup Lighting designed the lighting to back of house areas. The concept was to use artificial light in a sensitive way to reinforce the legibility of both the existing historic fabric and new architectural interventions, enhance the enjoyment of spaces in and around the buildings and provide a pleasing experience for the public after dark. Although historically the buildings were developed at different times, the development of the Spa complex has given this group of buildings a new unity. The lighting was designed in consideration of the whole site and aims to create a cohesive lit composition after dark and to reveal a contextural relationship between the predominantly Georgian and contemporary buildings that make up the development. The glazed facade of the new Royal Bath and the proximity of local residents provided a complex brief. One of the main challenges was to ensure that the development had a public presence at night and would make a positive contribution to the nightscape without having a detrimental impact on the local environment. Issues of light spill and light trespass were raised as a concern by the planners from very early on and were a key consideration throughout the project. The brightness of surfaces and amount of reflected light was very carefully controlled to minimise light spill and create subtle lighting effects. A condition was attached to the lighting with regards to Planning Permission and Listed Building Consent. In order to discharge the condition, the different lighting scenes that would be in operation during the course of a typical day had to be demonstrated to the planning officers and council members. The use of dimming and architectural lighting control was therefore fundamental in allowing the appearance of the finished scheme to be fine tuned. The planners were “impressed by the subdued quality of the lighting scheme and by the sensitivity shown for the amenities of adjoining residents in designing the lighting scenes for different times of day”, thereby allowing the condition to be discharged. External illumination to the buildings is very restrained. The soft warm colour of Bath sandstone is enhanced under gentle warm white illumination. On the whole lighting techniques were employed which provided precise illumination to key architectural details and historical features. Lateral light spill and glare is controlled through the use of louvres, cowls, baffles and other optical devices. The internal illumination is designed to create a calm and relaxing environment and to complement the simple geometric forms of the architecture. Emphasis is on the soft illumination of vertical surfaces with special lighting treatments to key features to provide drama and visual interest. The artificial lighting is designed to complement and supplement daylight in areas where natural light is present. Functional lighting is provided using long life energy efficient sources carefully integrated into the architecture to minimise visual clutter. A key part of the lighting concept is that the character of lighting is allowed to change from day through dusk and after dark creating different moods according to the time of day and operational requirements.

Cross BathLighting to the jewel like Cross Bath is soft, subtle and discreet. The main pilasters are front-lit and the entrance portico columns are back-lit to create a sillhouette. This is achieved by using in-ground uplights with warm white dimmable sources. All luminaires are fully adjustable and fully louvred to minimise glare. At high level the decorative urns are back and side-lit with miniature projectors in a concealed location to provide drama and focus. A soft wash to the frosted glazed screen is provided by the internal lighting. Internally, emphasis is on the low level illumination of vertical surfaces to create a sense of enclosure. The surrounding curved Bath stone walls and glazed screens are softly uplit from floor recessed fibre-optic heads. Underwater pool lights create a warm glow within the water whilst meeting safety and security requirements.

Hot BathThe external lighting to the Hot Bath provides a visual link to the Cross Bath with front-lighting to the pilasters and backlighting to the entrance portico columns in a similar manner. At roof level the internal face of the Hot Bath stone balustrade, visible from the pool through the glazed roof is illuminated with warm white light. This helps to draw one’s eye through the glazing which avoids it becoming a mirror after dark.Inside the Hot Bath, the stone cube containing the treatment rooms is uplit from a continuous linear fluorescent floor recessed lighting trough with a partially frosted glass diffuser. At the corners of the corridor, separately controlled white and midnight blue curved cold cathode is integrated within four small circular rooflights. General lighting is provided very simply by recessed downlights with dark light reflectors to minimise visual impact. Feature lighting is provided to highlight niches and other architectural features. Automatic control through the architectural lighting control system enables a change in atmosphere from day to night.

New Royal BathThe lighting to the highly glazed New Royal Bath was perhaps the most technically challenging aspect of the project. The external appearance is largely derived from the internal lighting and therefore the internal lighting was carefully conceived with this in mind. There is no direct illumination to the stone cube and it is illuminated purely by reflected light. Internal lighting to the lower ground Minerva Bath creates a natural diffuse glow on the frosted glass panels at the base of the building.The main pool concrete mushroom columns which support the cube are uplit through the water and ripples of light are projected onto the underside of the cube. In addition to this, architectural theatrical gobo projectors are concealed at high level and project green/blue coloured ripple patterns onto the pool surround to enhance the natural ripple effects. Clear glass lenses set within the cube and visible from outside softly glow from the general lighting within the areas behind. Lighting to the steam room is mainly concealed within architectural details. A continuous strip of LED’s concealed beneath the stone benches provides a perimeter glow. Within the steam pods a combination of high ambient temperature and harsh environmental conditions posed a real challenge. Fibre optics could not be incorporated due to structure. Therefore high performance tungsten halogen projectors fitted with blue glass filters and spread lenses were mounted beneath the benches to provide low level lighting and a glow within each pod. These were specifically tested for the project to ensure that they met the onerous requirements. The main focus of the steam room is a central waterfall shower which integrates a colour-change fibre optic lighting system. This infuses the water and fine mist with coloured light and creates a dynamic lit effect.The final and most dramatic space is the rooftop pool. Dramatic views are enjoyed across the city and light comes from the water alone. State of the art underwater LED pool lights with high power LED’s illuminate the pool to create a magical experience.